In the art of vacuum packed sealed food containers, it is common to use a glass jar or plastic or metal container, hereinafter referred to as "container", with a sealed reclosable cap or lid or closure such as a snap-on, snap-off closure or a twist-on, twist-off closure, hereinafter referred to as "closure". A partial vacuum in the container causes the closure to bow inwardly to form a slight concave configuration. When the closure is released from the container and atmospheric pressure enters the container, the closure pops upwardly, thereby providing a form of tamper evident seal. As a result of a resilient sealant between the closure and the container and the atmospheric pressure on the closure due to the vacuum within the container, it is sometimes difficult to force or untwist the closure to an open position, and substantial torque is required to unscrew or release a twist-off reclosable closure.
In one form of reclosable and snap-on closure for a vacuum container which has been used for packaging food, the center portion of the closure is provided with a small vent release opening. A resilient sealant material extends through the vent opening and is molded to form a small diameter flange or disk on the inside surface of the closure and a larger diameter disk or button on the top surface of the closure. When it is desired to open the vacuum container, the top button of the resilient material is peeled upwardly with the fingers to pull a stem of the resilient material through the vent hole and to tear a vent hole within the inner disk. This exposes the contents of the container to atmospheric pressure, after which the closure may be snapped from the container. The top button of resilient material is discarded, and the food contents of the container remain open to the atmosphere through the small vent opening. Thus the vent opening continues to permit the escape of moisture and vapor from the food product within the container and/or permits humidity in the atmosphere to enter the container and the food product within the container.
In the art of pressurized aluminum beverage cans or containers having a top end wall or shell with an E-Z open scored portion defining a hinged tab for forming a pour opening, it is known to provide a pressure release vent tab or button which is also defined by a smaller score line and hinge section, for example, as disclosed in U.S. Pat. No. 5,307,947. The pressure in the beverage container is released by depressing the vent tab or button down into the container so that the beverage does not squirt from the container when the pour tab is pivoted to its open position within the container. As disclosed in connection with FIG. 4 of the patent, a ring of resilient and elastic sealant material is applied on the inner surface of the top end wall or shell around the pressure release vent tab or button. The ring of sealant material is sheared when the vent tab is depressed into the container.
Other forms of food and beverage containers with reclosable sealing closures having vacuum release means in the form a pull tab or depressible button are disclosed in U.S. Pat. No. 2,046,227, No. 3,369,689, No. 3,410,436 and No. 3,446,383. In all of such containers and reclosable closures, it is highly desirable for the vent release means to be able to withstand pressure within the container as well as a partial vacuum within the container. For example, with food products which are cooked within a sealed container, the vent release means must be able to withstand the cooking pressure. After the food product cools, a partial vacuum is created within the container so that the vent release means must also be able to hold the vacuum within the container.
After a container is opened by actuating the vent release means and removing the closure and it is desired to reclose the container with the closure, it is highly desirable for the vent release means to prevent any gas or liquid from escaping out of the container or into the container, for example, when a container enclosing a liquid, is accidentally upset. Thus it is desirable to avoid any tearing or shearing of a resilient sealant material which is used to seal the closure to the container or to form the vent release means. That is, when the resilient sealant material is torn or sheared, it is difficult for the material to prevent the passage of gas or liquid through the material. The tearing of the resilient sealant material also produces fine fibers or hairs which are undesirable, especially in the environment of a food product. It is further desirable for the vent release means to be operable without the exposure of any sharp metal edges which may cut the fingers of a person gripping the container and closure. As apparent from a review of the above mentioned patents, none of the containers disclosed in the patents provide all of the above desirable features.